Method of producing asymmetrical currents from symmetrical alternating electromotive forces.



Patented Nov. 4, I902 I. l. PUPIN.

IETHOD 0F PRODUCING ASYIIETRICAL CUBBENTS F80. SYIETBICAL ALTERNATINGELECTBOIOTIVE FORCES.

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I. .Pupin Witne s s s Tnvfilglr- J WWW 4a b v m I I v I Aliarjy UNITEDSTATES PATENT OFFICE.

MICHAEL I. PUPIN, OF YONKERS, NE\V YORK.

METHOD OF PRODUCING ASYMMETRICAL CURRENTS FROM SYMMETRlCAL ALTERNATINGELECTROMOTIVE FORCES.

SPECIFICATION forming ert of Letters Patent No. 713,044, dated November4, 1902.

Application filed January 4, 1898. Renewed October 4, 1902. Serial No.125,991. (No specimens.)

To all whom it may concern.-

Be it known that I, MICHAEL I. PUPIN, a citizen of the United States ofAmerica, residing at Yonkers, county of \Vestchester, State of New York,have invented certain new and useful Improvements in Methods ofProducing Asymmetrical Currents from Symmetrical AlternatingElectromotive Forces, of which the following is a specification.

An asymmetrical current is a periodic current in which the total numberof coulombs flowing in one direction is greater than the total numberflowing in the opposite direc tion. Such a current will deflect apermanent magnet and be deflected by it and will produce electrolysis.It is equivalent to periodic unidirectional impulses equal to thedifierence between the number of coulombs transmitted in oppositedirections.

The improved method for producing an asymmetrical current in a circuitis to impress an alternating electromotive force upon the circuit andoppose thereto an electrometive reaction which is greater in onedirection than in the other. I thus construct a circuit which willot'feran asymmetrical impedance to a simple harmonic electromotiveforce. This electromotive reaction can be produced by placing in thecircuit a direct-current generator and a reversible, preferablynon-cumulative, electrolytic polarization-cell the capacity reactance ofwhich for the frequency of the electromotive force to be employed is aslarge as or preferably greater than the other reactances of the circuit.To get rectification of high efiiciency, the capacity reactance shouldbe about one hundred times as large as any other reactance of thecircuit. Upon this circuit I superimpose an alternating electromotiveforce. The direct-current generator-say a voltaic cell-'and apolarization-cell, which I shall call a simple electrolytic cell-say twoplatinum electrodes in dilute sulfuric acidtaken together constitute anasymmetrical electrolytic element which possesses an alternatingelectromotive reaction that is greater in one direction than I in theother. Such an element is the equivalent of a cell (which may also bedescribed, broadly, as'an element) which has the prop- .trode immersedin dilute sulfuric acid.

erty of developing a higher counter electromotive force when traversedby a current in one direction than when the current is reversed. Forexample, it is equivalent to a cell consisting of a zinc and a platinumelec- In such a cell the difference of potential between the twoelectrodes is not sufficient to overcome the counter electromotive forcedue to the decomposition of water, and hence it generates no current;but if an electromotivo force be impressed such a cell opposes a greatercounter electromotive force in one direction than in the other. It maybe pointed out here that none of these arrangements are efficient asrectifiers unless so directed that the electrolytic capacity of the cellis properly adjusted with respect to the frequency of the electromotiveforce employed, so as to give to the capacity reactance the magnitudeabove indicated.

In the accompanying drawings, which form a partof this specification,Figure 1 illustrates a system in which a direct-current generator and areversible non-cumulative polarizer are placed in the circuit. Fig. 2shows the arrangement of Fig. l as applied to multiplex telegraphy byresonance-circuits.

In Fig. 1 a generator E of alternating electromotive force of anyconvenient type is placed in series with a key F and the primary coil Gof a transformer. The key may be, for example, an ordinarytelegraph-key. Whenever it is closed, an alternating current flows inthe circuit E F G. This circuit may be of any convenient length, and, ifdesired, it may include a telegraphic main line, or the line may beinterposed between coils which are in inductive relation with coils Gand H, respectively. A coil H, forming the secondary coil of thetransformer G II, is placed in circuit in series with a primary cell K,a suitable magnetic relay-circuit closer P, and an electrolyticpolarization-cell containing two terminal wires, preferably of platinum,which 5 moved.

I trolytic cell.

7, capacity and small internal resistance.

distance apart is conveniently adjusted by heating and softening thecross-bar T, then placing a thin sheet of mica between the ends of thewires and bringing them in contact with it on opposite sides while thecross-bar cools and sets, afterwhich the mica is re- The exposed. endsof the wires are then immersed in a suitable electrolyte, as dilutesulfuric acid, and connected to the circuit, as shown. The cell thusformed will be non-storage or non-cumulative, because the gases willreadily bubble away from the small plates, and since it is of smallcapacity the full counter electromotive force is quickly attained. It iscapable of developing at its maximum about two volts counterelectromotive force of polarization.

The direct-electromotive-force generator K may be an ordinary primarycell.

-It is obvious that either the polarizationcell or the primary cell, orboth, may be replaced by batteries of cells in series; but the primarycell or battery should develop an electromotive force preferably equalto or slightly less than the maximum counter electromotive force of thepolarization-cell or battery of cells. The term cell will hereinafter beused to mean either a single cell or a battery of cells. The primarycell and the polarization-cell together prod uce no current; but whenthe key F is closed the alternate electromotive-force is also impresseduponv the circuit H A B K P. The counter electromotive force of theelectrolytic cell when charged to its full capacity will be equal to thedecomposition value of the electrolyte, and it is assumed that theelectrolytic cell develops at its maximum a counter electromotive forceabout. equal to that of the primary cell. Platinum electrodes in dilutesulfuric acid develop a counter electromotive force of about two volts.,Obviously with these two cells alone in the circuit there will be noconduction-current; but while the plates are receiving a charge what maybe called a condenser-current is flowing. After the plates have beenfully charged the two cells will balance each other; but the circuit hasthis peculiarity, speaking generally, that both the capacity-reactanceof the electrolytic cell and the electromotive force of the primarybattery will oppose an alternatingelectromotive forceduring one halfperiod and not during the other half period. The capacity of theelectrolytic cell can be diminished and its capacity-reactanceproportionately increased by reducing the size of the plates. If underthe conditions stated, with the electromotive force of the primary celland the counter electromotive force of the electrolytic cell balancedagainst each other, an alternating electromotive force is impressed uponthe circuit the circuit will have resistance reaction and self-inductionreactance when the phase of the alternating electromotive force is inthe same direction as the electromotive force of the primary cell, andwhen it is opposed the circuit, in addition tothese two reactances, willhave also'a capacity reactance. If, therefore, the capacity reactance bemade large in comparison with the other two reactances, thecurrentflowing in one direction will be large in comparison with the quantityflowing in the other direction. It is only necessary to make thecapacity reactance sufliciently large in order to make the currentconsist, practically, of a series of unidirectional impulses. Itis clearthat the values of the electromotive forces need not be in the ratiostated above, but may be in an y convenient ratio so long as the maximumelectromotive force developed in the polarization-cell is less than thesum of the o'thertwo electromotive forces when these have the same sign.be obtained an asymmetrical current.

It is not necessary to have a polarizationcell of thedescription givenabove. Any other polarization device having the properties heretoforestated may be substituted for either of the cells herein described. Itmust, however, be a cell the capacity of which is properly proportionedwith respect to the frequency of the impressed electromotive force, soas to give it a capacity reactance which is of the magnitude described,and for very efficient rectification the capacity reactance should be,say, as much as one hundred times as large as any of the otherreactances of the circuit.

This invention is of considerable value in several applicationsforpractical purposes, and its application to telegraphy by alternatingcurrents, and more particularly to multiplex telegraphy byresonance-receiving circuits, will now be described. The chiefdifficulty-in using alternating currents fol-telegraphy is that themagnetizing force of the current transmitted must, generally speaking,be relied on to produce the entire magnetic effect in the receivinginstruments, and

this magnetizing force, being proportional to the square of themagnetizing-current, falls olf rapidly when the current is diminished,

as it always is in transmission over long lines.

With direct currents, however, the currents transmitted can be'actedupon at the receiver by strong magnetic fields produced independently ofthese currents, as by powerful permanent magnets or electromagnets.Hence by the aidof this invention much stronger effects can be producedinthe receiving apparatus with a given impressed alternatingelectromotive force than is possible without the aid of the invention.

The application of the invention to teleg- Then there will always.

raphy without employing resonance effects is illustrated in Fig. 1. Inthis figure the armature P, which is placed between the poles of apowerful permanent magnet, operates a circuit-closer O, which closes alocal circuit in which is a battery M and a sounder N.

A system of multiple telegraphy by resonance receiving-circuits isillustratedin Fig. 2. A long telegraphic line L has at the transmittingend means for impressing on the line independently of each other andsimultaneously or otherwise several alternatingcurrentsofdifierentperiodicities. Forinstance, there may be severallocal transmitting-circuits, such as G F E of Fig. 1, acting upon theline through transformers like G H the secondary coils being connectedin the line in series. The different generators should generatealternating currents of diiferent periodicities. At the receiving endshould be several receiving resonance-circuits like R S G in which R andS are adjustable condensers and G is the primarycoil of a transformer G211. Each of these receiving-circuits should be tuned to resonance withone of the impressed electromotive forces. Connected With each is acircuit H A B K P for producing an asymmetrical current and arelay-circuit M N 0 like the similarly-lettered circuits in Fig. 1. Theadvantages of using a separate circuit H A B K P in addition to theresonance-circuit R S G is that it enables the construction of aresonancecircuit the electromagnetic constants of which are notappreciably afiected by the constants of the receiving instrument, sinceit need not be put in the resonance-circuit.

I have practiced the invention herein disclosed successfully inrectifying Hertzian oscillation, as well as oscillations of thefrequencies produced in ordinary commercial practice. \Vhen a circuit isproperly adjusted for a given frequency, it will effect even betterrectification with all lower frequencies. The converse is of course nottrue.

Many changes may be made without departing from the spirit of theinvention, and it is not limited to specific details herein shown.

I do not in this application make any claimsto the apparatus hereinshown for carrying out my hereinbefore-described method, as suchapparatus is claimed in another application filed by me in the UnitedStates Patent Office on the 8th day of September, 1900, and seriallynumbered 29,404, this lastnamed application being a division hereof.

What I claim, and desire to secure by Letters Patent of the UnitedStates, is

1. The method of producing an asymmetrical current in a circuit, whichconsists in impressing an alternating electromotive force upon thecircuit, and opposing thereto the electromotive reaction of anasymmetrical electrolytic element, the capacity reactance of which isproperly proportioned with respect to the other reactances of thecircuit for the frequency to be employed, substantially as described.

2. The method of producing an asymmetrical current in a circuit, whichconsists in impressing an alternating electromotive force upon thecircuit, and providing in the said circuit a direct-current generatorand a simple electrolytic cell, the capacity reactance of the simpleelectrolytic cell being properly proportioned with respect to the otherreactances of the circuit for the frequency of the alternatingelectromotive force employed, substantially as described.

Signed by me in the city of Yonkers, New York, this 23d day of December,1897.

MICHAEL I. PUPIN.

In presence of- THOMAS EWING, J r., SAMUEL W. BALCH.

